1. Field of the Invention
This invention relates to a magnetic head used in a magnetic recording device, and in particular, to a thin film magnetic head comprising at least one thin magnetic film.
2. Description of the Prior Art
The magnetic head is used for magnetically recording and/or reading information on a magnetic recording medium such as a magnetic tape, a magnetic disk, or the like.
Although a conventional magnetic head is a bulk type, the thin film magnetic head has been developed and come into actual use. Thin film magnetic heads of an inductive type are disclosed in, for example, U.S. Pat. No. 3,700,827 by Nagao assigned to Nippon Electric Company, Limited, and an article by Wakabayashi et al entitled "A THIN FILM MULTI-TRACK RECORDING HEAD" published in the IEEE TRANSACTIONS ON MAGNETICS, VOL. MAG-18, NO. 6, pages 1140-1142, November 1982. A thin film magnetic head of a magnetoresistive type is disclosed in, for example, U.S. Pat. No. 3,940,797 by Brock et al assigned to International Business Machines Corporation.
In the inductive type thin film magnetic head, at least one of magnetic members forming a magnetic headcore is formed in a thin film, and the two magnetic members are spaced apart from each other by a thin non-magnetic gap spacer layer to define a magnetic gap of the magnetic headcore.
In a certain type of the inductive type thin film magnetic head, a coil conductor and insulator layers are also formed as thin films.
Those thin film magnetic member or members, gap spacer layer, coil conductor and insulation layers are successively formed in a predetermined stacking sequence by the thin film forming technique such as the sputtering process. However, the use of the thin film forming technique has a disadvantage for a large-scaled production of magnetic heads.
In FIGS. 4a, 4b, and 5 in U.S. Pat. No. 3,700,827 as described above, a substrate having a thin film magnetic member is assembled and secured with another substrate having another thin film magnetic member and a gap spacer layer by use of adhesive, because the sputtered gap spacer layer does not have adhesive function.
A bonding glass has been known as a gap spacer material for the bulk type magnetic head. However, the bonding glass cannot be used as the magnetic gap for the thin film magnetic head because the bonding glass must be heat treated at a high temperature such as 400.degree. C.-500.degree. C. which badly affects the thin magnetic film so that the desired magnetic characteristic cannot be obtained.
In the magnetic head in FIG. 2 of U.S. Pat. No. 3,700,827 as described above, no guard plate is used. When the guard plate is desired, it cannot be directly bonded by use of the bonding glass.
In the above-described IEEE TRANSACTIONS ON MAGNETICS, a thick SiO.sub.2 layer is formed and the guard plate is bonded thereon by use of the bonding glass.
A thin magnetic film has a desired pattern according to a desired recording track. Therefore, a surface after formation of the thin magnetic film has a step portion along the outer contour of the pattern of the thin magnetic film. The step portion cannot be removed by the next successively sputtered layer.
The step is removed by the bonding glass layer in the magnetic head as disclosed in the IEEE TRANSACTIONS ON MAGNETICS as described above.
However, if the gap spacer layer can be formed by a material which does not badly affect the thin magnetic film and which has the adhesive function, the thin film magnetic head can be easily produced by adhering two previously formed parts by use of the gap spacer material without sputtering the gap spacer layer. The bonding glass layer for adhering the guard plate can be omitted so that the guard plate can be adhered to the gap spacer through the thick SiO.sub.2 layer sputtered thereon.
The magnetoresistive type magnetic head also comprises a gap spacer layer between a thin magnetic layer, that is, a magnetoresistive element and a magnetic shield. Any bonding layer is required to adhere the gap spacer layer and the magnetic shield. If any adhesive material, which does not badly affect the magnetoresistive element, can be used as the gap spacer layer, the sputtering process of the gap spacer layer can be advantageously omitted.